What is the power supply scheme of the rack in this case?

Question

Electronics

Good afternoon, help a neophyte understand the power supply circuit.
Before that, I met with schemes for ensuring power supply fault tolerance by using UPS. There are 2 electrical panels with automation in the server room, power comes to the panels from two substations + there are several diesel generators, from which a backup line goes to each panel. There is one line from each shield to each rack, but there are no UPS in the rack, but there are only ordinary rack pilots (without a button). How is fault tolerance implemented in this case? Why draw lines from two shields? After all, 1 pilot can be recorded with only 1 line? And if you put it in the pilot and record each from different shields, then the servers have 1 power supply with one output, why it can only be plugged into one pilot.
The main question is why in this case draw lines from 2 shields and how can they be combined?

Answer 1

2 lines pull for redundancy. If there is only one power supply in the equipment, then it is necessary to connect it through an automatic power switching device. Or through a UPS with two inputs, performing the function of auto power switching